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العروض التقديمية

Capacitorsالمكثفات -بعنوان تقديمي :عرض

الفيزياء للصف الثاني عشر العلمي

A uniform electric fieldis an electric field in which the

field strength does not vary. This givesa constant force on any charge that

exists in the field.

A uniform electric fieldis an electric field in which the

field strength does not vary. This givesa constant force on any charge that

exists in the field.

electric potential difference

= work per unit charge = force x distance per unit charge = force per unit charge x distance = electric field strength x distance

V = Ed V = Ed E = V/d, with units of volts/meter

CapacitorCapacitora device that stores charge

made of two conductors separated by an insulator

The amount of charge that acapacitor can store depends on:1. area of conducting surface2. distance between the conductors3. type of insulating material

link

Capacitancethe ratio of charge to potential difference

C = Q/V Q = CV

The SI unit of capacitanceis the Farad, F, named inhonor of Michael Faraday.

One Farad of capacitance means thatone Coulomb of charge may be stored

in the capacitor for each Volt of potential difference applied.

One Farad of capacitance means thatone Coulomb of charge may be stored

in the capacitor for each Volt of potential difference applied.

Capacitor CircuitsSeries

1. reciprocal of the total capacitance is the sum of the reciprocals of the separate capacitors

1/CT = 1/C1 + 1/C2 + 1/C3 + ...

2. charge is the same on each capacitorQT = Q1 = Q2 = Q3 = ...

3. total potential difference is the sum of each

VT = V1 + V2 + V3 + ...

In other words, in a series circuit,capacitance adds as reciprocals,

charge stays the same,and voltage adds.

C1

C2

C3

E = 12 V

CT =

VT =

QT =

C1

C2

C3

C,mF

V,V

Q,mC

12

10

15

C1

C2

C3

E = 12 V

CT = 4.0 mF

VT = 12 V

QT = 48 mC

C1

C2

C3

C,mF

V,V

Q,mC

12

10

15

48

48

48

4.0

4.8

3.2

Parallel1. total capacitance is the sum of each separate capacitor CT = C1 + C2 + C3 + ...

2. total charge is the sum of the charges on each separate capacitor

QT = Q1 + Q2 + Q3 + ...3. potential difference is the same across each capacitorVT = V1 = V2 = V3 = ...

In other words, in a parallel circuit,

capacitance and charge add, but voltage stays the same.

C3

E = 12 V

CT =

VT =

QT =

C1

C2

C3

C,mF

V,V

Q,mC

8

10

4C2

C1

C3

E = 12 V

CT = 22 mF

VT = 12 V

QT = 264 mC

C1

C2

C3

C,mF

V,V

Q,mC

8

10

4C2

C1

12

12

12

96

120

48

Capacitors are often used in conjunctionwith resistors in simple circuits that arecalled RC Circuits.

Click here and here to view computersimulations of this type circuit.

Explore this link to learnmore about capacitors.